Dissolvable microneedles for transdermal drug delivery showing skin pentation and modified drug release.

Topical therapies for chronic skin diseases suffer from a low patient compliance due to the inconvenient treatment regimens of available products. Dissolvable microneedles (MN) with modified release offer an interesting possibility to increase the compliance by acting as a depot in the skin and thereby decreasing the dosing frequency. Furthermore, the bioavailability can be increased significantly by bypassing the barrier of the skin by the direct penetration of the MN into the skin. In this study the depot effect and skin penetration of an innovative dissolvable MN patch was assessed by insertion in ex vivo human skin and in vivo using minipigs. The MN patches are based on biodegradable polymers and the active pharmaceutical ingredients calcipotriol (Calci) and betamethasone-17-21-dipropionate (BDP) used to treat psoriasis. Using computed tomography (CT) and Coherent anti-Stokes Raman scattering (CARS) microscopy it was possible to visualize the skin penetration and follow the morphology of the MN as function of time in the skin. The depot effect was assessed by studying the modified in vitro release in an aqueous buffer and by comparing the drug release of a single application of a patch both ex vivo and in vivo to daily application of a marketed oleogel containing the same active pharmaceutical ingredients. The CT and CARS images showed efficient penetration of the MN patches into the upper dermis and a slow swelling process of the drug containing tip over a period of 8 days. Furthermore, CARS demonstrated that it can be used as a noninvasive technique with potential applicability in clinical settings. The in vitro release studies show a release of 54% over a time period of 30 days. The pharmacological relevance of MNs was confirmed in human skin explants and in vivo after single application and showed a similar response on calcipotriol and BDP mediated signaling events compared to daily application of the active oleogel. Altogether it was demonstrated that the MN can penetrate the skin and have the potential to provide a depot effect.

MALDI imaging facilitates new topical drug development process by determining quantitative skin distribution profiles.

Generation of skin distribution profiles and reliable determination of drug molecule concentration in the target region are crucial during the development process of topical products for treatment of skin diseases like psoriasis and atopic dermatitis. Imaging techniques like mass spectrometric imaging (MSI) offer sufficient spatial resolution to generate meaningful distribution profiles of a drug molecule across a skin section. In this study, we use matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) to generate quantitative skin distribution profiles based on tissue extinction coefficient (TEC) determinations of four different molecules in cross sections of human skin explants after topical administration. The four drug molecules: roflumilast, tofacitinib, ruxolitinib, and LEO 29102 have different physicochemical properties. In addition, tofacitinib was administrated in two different formulations. The study reveals that with MALDI-MSI, we were able to observe differences in penetration profiles for both the four drug molecules and the two formulations and thereby demonstrate its applicability as a screening tool when developing a topical drug product. Furthermore, the study reveals that the sensitivity of the MALDI-MSI techniques appears to be inversely correlated to the drug molecules' ability to bind to the surrounding tissues, which can be estimated by their Log D values. Graphical abstract.

Combination of MALDI-MSI and cassette dosing for evaluation of drug distribution in human skin explant.

Study of skin penetration and distribution of the drug compounds in the skin is a major challenge in the development of topical drug products for treatment of skin diseases. It is crucial to have fast and efficacious screening methods which can provide information concerning the skin penetration and the distribution of the drug molecules in the region of the target. Mass spectrometry imaging (MSI) such as matrix-assisted laser desorption/ionization (MALDI)-MSI offers the opportunity to analyze the drug distribution at micrometer scale, but is a low throughput technique. Cassette dosing of drug molecules has been widely used for two decades as a high throughput screening tool for plasma pharmacokinetic analysis. The purpose of this study is to evaluate the utility of combining MALDI-MSI with cassette dosing to obtain a medium throughput screening technique for drug distribution in the skin directly from thin tissue sections. Excised fresh human skin was treated with two different formulation types containing both single drugs and a cassette with four drugs. Biopsies were taken and analyzed with traditional UHPLC-MS/MS and MALDI-MSI. The results reveal that skin penetration data of the four drugs administered together were in agreement with skin penetration data obtained when the molecules were administered individually. Furthermore, the MALDI-MSI data reveal different distribution profiles of the four drugs which were not possible to deduce from the UHPLC-MS/MS bioanalysis. These findings suggest that combination of MALDI-MSI and cassette dosing can be used as a medium throughput screening tool at an early stage in the drug discovery/development process. Graphical abstract Investigation of drug distribution in human skin explant by MALDI-MSI after cassette dosing.

Imaging of distribution of topically applied drug molecules in mouse skin by combination of time-of-flight secondary ion mass spectrometry and scanning electron microscopy.

In the development of topical drugs intended for local effects in the skin, one of the major challenges is to achieve drug penetration through the external barrier of the skin, stratum corneum, and secure exposure to the viable skin layers. Mass spectrometric imaging offers an opportunity to study drug penetration in a variety of skin models by mapping the spatial distribution in different skin layers after topical application of the drug. In this study, we used time-of-flight secondary ion mass spectrometry (TOF-SIMS) and scanning electron microscopy (SEM) to image the distribution of three drug molecules in skin tissue cross sections of inflamed mouse ear. The three compounds, roflumilast, tofacitinib, and ruxolitinib, were topically administered to the mouse ears, which were subsequently cryosectioned and thawed for the analyses. The results reveal that the combination of TOF-SIMS and SEM was beneficial for interpretation of drug distribution. SEM identified the different skin layers, while spatial distributions of all three compounds could be visualized by TOF-SIMS, showing that the drug was primarily distributed into, or on the top of, the stratum corneum. Imaging of endogenous skin components like cholesterol, phospholipids, ceramides, and free fatty acids showed distributions in good agreement with the literature. One limitation of the TOF-SIMS method is sensitivity, typically allowing for analysis in the millimolar range rather than the pharmacologically relevant micromolar range. However, the data presented demonstrate the potential of the technique for studying the penetration of drugs with different physicochemical properties in skin.

Structural study of four complexes of the M-N2S2 type derived from diethylphenylazothioformamide and the metals palladium, platinum, copper and nickel.

The four electron-transfer complexes trans-(di(N,N-diethyl-(2-phenyldiazenyl)thioformamide-kappaS,kappaN2))nickel, trans-(di(N,N-diethyl-(2-phenyldiazenyl)thioformamide-kappaS,kappaN2))copper, trans-(di(N,N-diethyl-(2-phenyldiazenyl)thioformamide-kappaS,kappaN2))palladium and trans-(di(N,N-diethyl-(2-phenyldiazenyl)thioformamide-kappaS,kappaN2))platinum have been crystallized, and their structures have been determined at low temperature. All the complexes are of the M-N2S2 type. The crystals of both the nickel and the copper complex belong to the tetragonal P4(1)2(1)2 system, in which the central metal ion lies on a twofold axis. The tetrahedral molecular symmetry around the central metal ion is unusual for the M-N2S2 electron-transfer complexes. The crystals of the palladium and platinum complexes on the other hand belong to the monoclinic C2/c system in which the metal ion lies on an inversion centre. The molecular symmetry around these metal ions is square planar. It is demonstrated that the pi electron density in the ligand planes has a high degree of delocalization. Furthermore, unusually large line broadening of the 1H NMR spectra was observed and investigated as a function of temperature for the palladium complex.

Solution and solid state 13C NMR and X-ray studies of genistein complexes with amines. Potential biological function of the C-7, C-5, and C4'-OH groups.

Parent genistein and its new amine complexes with morpholine and piperazine were studied comparatively in the solid and liquid states by X-ray crystallography and 13C and 15N NMR spectroscopy. Biochanine A and its complexes were used as reference. Secondary deuterium isotope effects on 13C chemical shifts in solution were studied in parent isoflavones and their morpholine and piperazine complexes to aid in evaluation of the electronic distribution in both systems. In addition, to quantify the extent of proton transfer as well as to establish strong hydrogen bonding of the 7-OH group in a morpholine complex, proton transfer from the 7-OH group to the piperazine nitrogen atom was also confirmed by 13C NMR in the solid state and by X-ray studies. The effect of 7-OH deprotonation yields a high frequency shift of 7-8 ppm on the C-7 carbon atom of the piperazine complex whereas it is as large as 12 ppm in the morpholine complex in the solid. The former trend is confirmed from solution state concentration studies which also show that the isoflavones have a strong tendency to form complexes with bases. Depending on the pKa difference between the isoflavones and the base this leads either to proton transfer and ion-pair formation or, in the case of a larger pKa difference, to a hydrogen bonded ion pair. The concentration studies show formation of a 1:1 genistein-piperazine complex in DMSO. Addition of water leads to formation of solvent separated ions. The C-5 OH group is involved in strong intramolecular hydrogen bonding leading to a pseudo aromatic ring extending the aromatic part of the drug pharmacophore. The analysis also suggests the way that both the C-7 and C-4' hydroxyl group of genistein may participate in stabilising the ternary inhibitor complexes of tyrosine-specific kinases or DNA topoisomerase II.